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As you probably know, any signal that is sent without wires is called a radio transmission. A common example is that the radio in your car receives transmissions. Similarly, a standard cell phone works by receiving—and transmitting—radio signals. Every device that broadcasts a radio transmission does so at a particular frequency, which is the oscillations, or movement from peak to trough, of the electromagnetic wave created by the transmission.

The entire set of radio frequencies is known as the radio spectrum. Contiguous portions of the radio spectrum are called bands, as in "the FM band." Radio frequencies describe the oscillations of a radio wave. For example, if you are tuned to an FM radio station at 92.5, it means that the radio transmission is oscillating at 92.5 megahertz per second. 92.5 megahertz (pronounced "may-ga-hurts" and abbreviated MHz) means that the radio transmission wave oscillates, or moves from its valley to its peak, at a rate of 92,500,000 times per second. If you think of this as listening from a distance to a really rapidly vibrating tuning fork, you have the right picture. The AM radio spectrum was developed before the FM spectrum, so it is lower down the spectrum, ranging from 535 kilohertz to 1.7 megahertz, or 535,000 to 1,700,000 oscillations per second. For example, 720 on the AM dial means that your radio receiver is tuned to a frequency of 720,000 oscillations per second. There are frequencies above, or higher than, the FM frequency as well as below it.

In fact, as I'll explain in a moment, Wi-Fi transmissions run at some of these higher frequencies. One thousand megahertz is equal to one gigahertz (pronounced "gig-a-hurts" and abbreviated GHz). So when you refer to the 2.4GHz frequency, you are actually talking about 2,400,000,000 (2.4 billion) oscillations per second. There are only so many frequencies in the radio spectrum that can be used for transmissions. This has inevitably led to the potential for conflicts about usage, as well as attempts to dominate particular frequencies.